<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>2-3 border</title>
  <style>
    .wrapper {
      display: flex;
    }

    .box1 {
      width: 0;
      height: 0;
      /*  上右，注意设置的尺侧   */
      border-top: 100px solid #e55039;
      border-right: 100px solid transparent;
      /* 左下也可以 */
      /* border-left: 100px solid #e55039;
    border-bottom: 100px solid transparent; */
    }


    .box2 {
      width: 0;
      height: 0;
      /* 左上 */
      border-left: 100px solid transparent;
      border-top: 100px solid #a0e71c;
      /* 右下也可以 */
      /* border-right: 100px solid #a0e71c;
    border-bottom: 100px solid transparent; */

    }

    .box3 {
      width: 0;
      height: 0;
      /* 下左 */
      border-bottom: 100px solid #17c27b;
      border-left: 100px solid transparent;
      /* 上右也可以 */
      /* border-top: 100px solid transparent;
    border-right: 100px solid #17c27b; */
    }

    .box4 {
      width: 0;
      height: 0;
      /* 下右 */
      border-bottom: 100px solid #a224a7;
      border-right: 100px solid transparent;
      /* 左上也可以 */
      /* border-left: 100px solid #a224a7;
    border-top: 100px solid transparent; */
    }
  </style>
</head>

<body>
  <div class="wrapper">
    <div class='box1'></div>
    <div class='box2'></div>
    <div class='box3'></div>
    <div class='box4'></div>
  </div>
</body>

</html>